Angela Merkel has called on major internet platforms to divulge the secrets of their algorithms, arguing that their lack of transparency endangers debating culture.

The German chancellor said internet users had a right to know how and on what basis the information they received via search engines was channelled to them.

Speaking to a media conference in Munich, Merkel said: “I’m of the opinion that algorithms must be made more transparent, so that one can inform oneself as an interested citizen about questions like ‘what influences my behaviour on the internet and that of others?’.

“Algorithms, when they are not transparent, can lead to a distortion of our perception, they can shrink our expanse of information.”

An algorithm is the formula used by a search engine to steer a request for information. They are different for every search engine, highly secret and determine the significance or ranking of a web page.

Merkel has joined a growing number of critics who have highlighted the dangers of receiving information that confirms an existing opinion or is recommended by people with similar ideas.

“This is a development that we need to pay careful attention to,” she told the conference, adding that a healthy democracy was dependent on people being confronted by opposing ideas.

“The big internet platforms, through their algorithms, have become an eye of a needle which diverse media must pass through [to access their users],” she said.

There has been increasing concern about so-called filter bubbles and echo chambers – the result of an internet search in which an algorithm supposes the information someone would like to see based on previous searches, as well as information it might have about their location or preferences – in the light of the growing strength of populist movements in Europe, the Brexit vote in the UK and the rise of Donald Trump in the US. This month, President Barack Obama’s former social media adviser Caleb Gardner highlighted the danger of filter bubbles – a phrase invented by the internet activist Eli Pariser.

“More likely than not, you get your news from Facebook,” Gardner told students at Northwestern University in Illinois. “Forty-four per cent of US adults get news on the site, and 61% of millennials … if that doesn’t frighten you, you don’t know enough about Facebook’s algorithm. If you have a parent who’s a Trump supporter, they are seeing a completely different set of news items than you are.”

Merkel will have an eye on next year’s federal election in which she is expected to stand for a fourth term. The concern that the phenomenon of narrow debate which has been seen during the US presidential campaign might be replicated in Germany is one shared across Germany’s established parties.

Merkel called the issue a “challenge not just for political parties but for society as a whole”. If it was unclear what mechanisms were being used, it could “lead to a distortion of how people perceive things”, she said.

Thomas Jarzombek, the digital policy spokesperson of Merkel’s Christian Democratic Union, told Spiegel Online he did not think she was advocating that companies such as Google and Facebook should disclose company secrets, “but we do need more information from these operators as to how their algorithms function generally speaking”.

A cross-party working group is compiling recommendations urging more openness by internet platforms, including making details on how their algorithms collect, choose, evaluate and present information available to users. Its recommendations will be sent to Brussels, for the EU digital commissioner Günther Oettinger to work them into guidelines by next year. Oettinger told Spiegel Online: “Merkel has touched on an important topic.” But he said questions about search engines’ transparency had to “first undergo a more in-depth examination”.